3.2 Cells immunity Flashcards
define antigen
- recognised as nonself/foreign by immune system
- will stimulate immune response +production of antibodies
antigens are specific so immune system can identigy
- pathogens
- cells from other organisms of same species
- abnormal body cells
- toxins released from bacteria
describe phagocytosis
- phagocyte recognises foreign antigens on pathogen + binds to antigen, is attracted to pathogen by chemotaxis
- phagocyte engulfs pathogen surrounding it with its cell surface membrane
- pathogen contained in vacuole of cytoplasm of phagocyte
- lysosyme fyses with phagosome + releases hydrolytic enzymes into phagosome
- these hydrolyse pathogen
- phagocyte becomes antigen presenting cell + stimulates immune response
describe the cellular response
- T lymphoyctes recognise antigen presenting cells after phagocytosis
- specific T helper cells with receptor complementary to specific antigen binds to it, becoming activated + dividing by mitosis to form clones whicb
- stimulate B cells for humoral response
- stimulate cytotoxic T cells to kill infected cells by producing perforin
- stimulate phagocytes to engulf pathogens by phagoctyosis
describe the humoral response
- clonal selection
- specific B cells bind to antigen presenting cells +stimulated by T h cells
- divides rapidly by mitosis undergoing clonal selection - some become B plasma cells - secrete monoclonal antibodies
- some becom B memory cells - for secondary immune response
what is the primary response
- antibodies produced slower + low conc
- not many B cells to make antibodies
- Th cells need to activate B plasma cells
- symptoms shown
what is the secondary response
- produces antibodies faster + higher conc
- B + T memory cells present
- B memory cells undergo mitosis quicker/ quicker clonal selection
what are antibodies
- quaternary structure protein
- secreted by B cells
- binds to specific antigens
describe + explain how structure of antibody is related to its function
primary structure - sequence of amino acids in polypeptide chain
- determines folds in secondary structure
- determines specfic shape of tertiary structure + position of bonds
quaternary structure - 4 polypeptide chains
- enables specific shaped variable region
how do antibodies work to destroy pathogens
binds to two pathogens at the same time
enables antibodies to clump pathogens together - agglutination
phagocytes bind to antibodies + phagocytose many pathogens at once
what is vaccination
- injected antigens
- from attenuated pathogens
- stimulates formation of memory cells
- vaccine can lead to symptoms
how does the use of vaccines provide protection of individuals against disease
- normal response, memory cells produced
- on reinfection, antibodies produced faster + higher conc
- destruction of pathogen before any harm
how does the use of vaccines provide protection of populations against disease
- herd immunity
- makes it more difficult for pathogen to spread through population
- more people immune for fewer people carry disease
- fewer susceptible so less likely non vaccinated individual will come into contact with infected person + pass on disease
what is active immunity
- initial exposure to antigen
- memory cells involved
- antibody produced secreted by B plasma cells
- slow
- long term
what is passive immunity
- no exposure to antigen
- no memory cells involved
- antibody introduced into body i.e breast milk
- fast
- short term, antibody broken down
ethical issues of vaccines
- tested on animals, can feel pain
- tested on humans , unnecessary risk
- side effects
- expensive
effect of antigen variability on disease
- change in antigen shape due to genetic mutation
- not recognised by B memory cells = no antibodies
- not imune
- reungerdo primary response - slow release/ low conc of antibodies
- symptoms of disease
effect of antigen variability on disease prevention
- change in anitgen shape due to genetic mutation
- exisiting antibodies unable to bind to changed antigens
- immune system wont recognise different antigens
what is a successful vaccination programme
produce suitable vaccine -effective - make memory cell -no major side effects -low cost -easily produced/transported/stored/administered provides herd immunity
use of monoclonal antibodies
monoclonal antibody - antibody produced from single group of genetically identical B cells
bind to specific complementary antigen
- have a binding site/variable region with a specific tertiary structure
- only one complementary antigen will fit
replication of HIV in T h cells
- HIV infects T h cells
- HIV attachment protein attaches to receptor on T h cell membrane - Virus lipid envelope fuses with cell surface membrane + capsid released into cell, releasing RNA + reverse transcriptase
- Viral DNA made from viral RNA
- reverse transcriptase produces complementary viral DNA strand from viral RNA template
- double stranded DNA made - viral DNA into host DNA
- host cell enzymes used to make viral proteins from viral DNA
- viral proteins assembled with viral RNA to make a new virus
- new virus buds from cell, taking some cell surface membrane as envelope
- kills T h cells
- most host cells infected + process repeats
how does HIV cause AID symtoms
infected + kills T h cells
- T h cells cant stimulate cytotoxic T cells, B cells, phagocytes
- immune system deteriorates
- more susceptible to infections
- disease that wouldnt cause serious problems in healthy immune system are deadly
why are antibiotics ineffective against viruses
- antibioticd cant enter human cells - virus exists in host cells
- virus dont have own metabolic reactions which antibiotics target
